import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TcpEchoServer {
    //severSocket相当于外场拉客的，只有一个
    //clientSocket相当于内场服务的，每个客户端都会分配一个
    private ServerSocket serverSocket=null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket=new ServerSocket(port);
    }

    public void start() throws IOException {
        ExecutorService executorService= Executors.newCachedThreadPool();
        System.out.println("服务器启动：");
        while (true){
            Socket clientSocket=serverSocket.accept();
            //如果直接调用，该方法会影响这个循环的二次执行，导致accept不及时了
            //创建新的线程，用新的线程来调用processConnection
            //每次来一个新的客户端都搞一个新的线程即可
//            Thread t=new Thread(()->{
//                try{
//                    processConnection(clientSocket);
//                }catch (IOException e){
//                    e.printStackTrace();
//                }
//            });
//            t.start();
            executorService.submit(new Runnable() {
                @Override
                public void run() {
                    try{
                        processConnection(clientSocket);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            });
        }
    }

    //通过这个方法来处理一个连接
    //读取请求
    //根据请求计算响应
    //把响应返回给客户端
    public void processConnection(Socket clientSocket) throws IOException{
        System.out.printf("[%s:%d] 客户端上线！\n",clientSocket.getInetAddress().toString(),
                clientSocket.getPort());
        try (InputStream inputStream=clientSocket.getInputStream();
             OutputStream outputStream=clientSocket.getOutputStream()){
            Scanner sc=new Scanner(inputStream);
            PrintWriter printWriter=new PrintWriter(outputStream);
            while (true){
                //1.读取请求
                if(!sc.hasNext()){
                    //读取的流到了结尾了（对端关闭了）
                    System.out.printf("[%s:%d] 客户端下线了！\n",clientSocket.getInetAddress().toString(),
                            clientSocket.getPort());
                    break;
                }
                //直接使用sc读取一段字符串
                String request=sc.next();
                //2.根据请求计算响应
                String response=process(request);
                //3.把响应写回给客户端，响应里也要带上换行的
                printWriter.println(response);
                printWriter.flush();
                System.out.printf("[%s:%d] req: %s; resp: %s\n",clientSocket.getInetAddress().toString(),
                        clientSocket.getPort(),request,response);
            }
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            clientSocket.close();
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer tcpEchoServer=new TcpEchoServer(9090);
        tcpEchoServer.start();
    }
}
